Yahoo plans to ignore "Do Not Track" privacy requests sent by Microsoft's Internet Explorer (IE10) browser, calling its ally's unilateral decision "signal abuse" and pointing to a possible rift between the search partners.

One Do Not Track (DNT) expert, however, didn't think Yahoo's decision, announced last week, would affect its deal with Microsoft.

"I don't think this is especially significant," said Justin Brookman, director of consumer privacy at the Center for Democracy and Technology. "Yahoo! is just the biggest individual company to draw this line in the sand. I doubt this will affect their search relationship." Brookman has been heavily involved in the DNT standard-setting effort.

Dan Olds, an analyst with the Gabriel Consulting Group, agreed. "This won't rise to the level where it will affect the Yahoo-Microsoft relationship. Companies this large are able to compartmentalize."

IE10, which launched Oct. 26 alongside Windows 8 and will be released as a preview for Windows 7 by mid-November, is the only browser that has switched on Do Not Track (DNT) by default.

In reality, some argue, IE10 does not actually switch DNT on: In August, Microsoft backed away a step, and promised that during Windows 8 setup, customers will be notified of the impending setting and given a chance to turn it off.

Do Not Track (DNT) signals whether a user wants online advertisers and websites to track his or her movements. Four of the five major browsers -- Firefox, IE, Opera and Safari -- can now send a DNT signal, while Chrome will include the option by the end of this year. All but IE, however, initially leave it in the "off" position and require users to manually turn on the signal.

Like others -- primarily advertisers, but also some browser makers such as Firefox's Mozilla -- Yahoo criticized the on-by-default setting in IE10.

"In principle, we support DNT," Yahoo said in an unattributed entry on its policy blog Friday. "[But] Microsoft unilaterally decided to turn on DNT in Internet Explorer 10 by default, rather than at users' direction. It basically means that the DNT signal from IE10 doesn't express user intent. We will not recognize IE10's default DNT signal on Yahoo! properties at this time."

Online advertisers have balked at the idea that browsers can turn on DNT without asking users, essentially hoping that the under-consideration standard will not be widely adopted if the signal must be manually switched on.

Yahoo alluded to that on its blog, saying, "In our view, [IE10's on-by-default] degrades the experience for the majority of users and makes it hard to deliver on our value proposition to them."

"Value proposition" clearly refers to the trade-offs -- users must accept the targeted ads as the price for receiving free software, services and content -- that advertisers say make the Internet what it is. As far as advertisers are concerned, tracking is required to provide targeted ads.

A group composed of advertisers, browser makers, privacy advocates and others have not finalized a DNT standard, even after months of intensive work. The Worldwide Web Consortium (W3C) standards-setting group has, however, preliminarily ruled that browser makers cannot set the DNT signal for users, essentially letting each website decide whether it will acknowledge or ignore IE10's.

Advertisers recently turned up the rhetoric about DNT. Earlier this month, the Association of National Advertisers (ANA), an industry lobbying group, said Microsoft's decision would "harm consumers, hurt competition, and undermine American innovation," and called the on-by-default setting "unacceptable."

Privacy advocates countered, saying that the ANA's demands were "bizarre."

Yahoo's decision to ignore IE10's DNT signal is notable because the California company is allied with Microsoft in search. In 2010, the two firms signed a 10-year agreement whereby Yahoo's search results are fueled by Microsoft's Bing search engine.

If users choose "Customize," they can toggle off Do Not Track during Windows 8's setup process.